The emerald rockcod (''Trematomus bernacchii''), also known as the emerald notothen is a species of marine

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...

belonging to the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Nototheniidae : ''In some scientific literature, the term "cod icefish" is used to identify members of this family. This should not be confused with the term "icefish," which refers to the "white-blooded" fishes of the family Channichthyidae. See Icefish (disam ...

, the notothens or cod icefishes. It is native to the

Southern Ocean The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60° S latitude and encircling Antarctica. With a size of , it is regarded as the second-small ...

where it is a commercially important

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

Taxonomy

The Emerald rockcod was first formally described in 1902 by the Belgian-born British

ichthyologist Ichthyology is the branch of zoology devoted to the study of fish, including bony fish ( Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 33,400 species of fish had been described as of Octobe ...

George Albert Boulenger George Albert Boulenger (19 October 1858 – 23 November 1937) was a Belgian-British zoologist who described and gave scientific names to over 2,000 new animal species, chiefly fish, reptiles, and amphibians. Boulenger was also an active botani ...

with the type localities given as Cape Adare in Antarctica at a depth of 5-8 fathoms and Duke of York Island at a depth of 3-4 fathoms. In 1982 the Russian ichthyologist

Arkady Vladimirovich Balushkin Arkady (russian: Арка́дий, Arkadiy) is a Slavic masculine given name, ultimately derived from the Greek name Αρκάδιος, meaning “from Arcadia”. The Latin equivalent is Arcadius. Notable people with the name include: People: *Ark ...

placed this species, and all the other species in its

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

bar the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

, '' T. newnesi'', in the new genus ''Pseudotrematomus'' but this has not been widely accepted. The specific name honours the Australian Australian

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate caus ...

and

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, natural satellite, moons, comets and galaxy, g ...

Louis Bernacchi Louis Charles Bernacchi (8 November 1876 – 24 April 1942) was an Australian physicist and astronomer best known for his role in several Antarctic expeditions. Early life Bernacchi was born in Belgium on 8 November 1876 to Italian pare ...

who carried out much of the exploring and collecting of specimens during the

Southern Cross Expedition The ''Southern Cross'' Expedition, otherwise known as the British Antarctic Expedition, 1898–1900, was the first British venture of the Heroic Age of Antarctic Exploration, and the forerunner of the more celebrated journeys of Robert Falcon Sc ...

, on which the type was collected.

Description

This species is mostly brown in color with darker spots. The first

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

contains 4-6 spines, the second dorsal fin has 34-39 soft rays and the

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

has 31-35 soft rays. Females of this species can reach a length of , while males only reach . The maximum reported age for this species is 10 years.

Distribution, habitat, and habits

This species is native to the

on the seafloor at depths from very shallow waters to . It is adapted to living in waters of extremely low temperature (-1.86 °C mean temperature in

McMurdo Sound McMurdo Sound is a sound in Antarctica. It is the southernmost navigable body of water in the world, and is about from the South Pole. Captain James Clark Ross discovered the sound in February 1841, and named it after Lt. Archibald McMurdo o ...

). It consumes various

invertebrates Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

and small fishes and also is known to feed on some

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

. Their foraging techniques make them the primary predators of the medium-sized population of the Antarctic scallop, ''

Adamussium colbecki The Antarctic scallop (''Adamussium colbecki'') is a species of bivalve mollusc in the large family of scallops, the Pectinidae. It was thought to be the only species in the genus ''Adamussium'' until an extinct Pliocene species was described ...

''.

Physiological adaptations for cold

Unlike most organisms, the emerald rockcod does not show a typical heat shock response; for example, it does not upregulate the

heat shock protein Heat shock proteins (HSP) are a family of proteins produced by cells in response to exposure to stressful conditions. They were first described in relation to heat shock, but are now known to also be expressed during other stresses including expo ...

gene hsp70 when in warm temperatures. Instead, upregulation of

hsp70 The 70 kilodalton heat shock proteins (Hsp70s or DnaK) are a family of conserved ubiquitously expressed heat shock proteins. Proteins with similar structure exist in virtually all living organisms. Intracellularly localized Hsp70s are an importa ...

is more prominent when it is in its normal temperature environment. Although normally hsp70 is an inducible gene, this gene was found to be expressed at all times in emerald rockcod. A constitutive heat shock gene hsc71 showed the same pattern of expression, and so it was deduced that in the emerald rockcod hsp70 was also being expressed as a constitutive gene. Low temperatures in its Antarctic habitat may cause cellular stress that can denature the cellular proteins of these fish, making it necessary to express high constitutive levels of heat shock proteins.

References

{{DEFAULTSORT:rockcod, emerald emerald rockcod Fish of the Southern Ocean Fish of Antarctica emerald rockcod Taxa named by George Albert Boulenger